Method for estimating direction of person standing still

ABSTRACT

The invention is directed to detecting a boundary position between a foot and a lower leg of a person in an image acquired by an imaging unit, the boundary position being a substantial boundary part, in a lower limb, between the foot, which is a part from a malleolus to a tip part, and the lower leg; detecting a feature quantity that makes it possible to classify a ground and a part other than the ground in the image; setting, in a peripheral region around the boundary position, a plurality of local regions having positional information and/or direction information relative to the boundary position, and determining whether each of the local regions is the ground or the part other than the ground by using the feature quantity unique to the ground; determining a foot region from the local region determined as the part other than the ground; and estimating a direction of the foot of the person from the local region classified as the foot region and from the information.

TECHNICAL FIELD

The present invention relates to a method for estimating a direction ofa person standing still.

BACKGROUND ART

It is necessary for an autonomous mobile apparatus to determine a movingdirection of a person in order to move forward safely and effectively.

As a background art in the present technical field, there is JP2007-229816 A (PTL 1). In PTL 1, a method for predicting a course of apedestrian from a toe image is described. In the method, a pedestriancourse model construction unit constructs a course model of a generalpedestrian in advance by combining information of a toe image of aspecific pedestrian and detected course information of the specificpedestrian, and a pedestrian course model storage unit storesinformation of the pedestrian course model.

Then, a pedestrian course prediction unit predicts a course of anunspecific pedestrian by collating information of a toe image of theunspecific pedestrian, which image is generated by a pedestrian toeimage generation unit, and the information of a pedestrian course modelstored in the pedestrian course model storage unit.

As a method to detect a course in construction of a pedestrian coursemodel, it is described to detect a three-dimensional position of apedestrian serially in certain time intervals and to detect the courseof the pedestrian from a temporally change of the three-dimensionalposition.

CITATION LIST Patent Literature

PTL 1: JP 2007-229816 A

SUMMARY OF INVENTION Technical Problem

In PTL 1, a pedestrian course model is constructed from a positionalchange of a pedestrian in predetermined time intervals. However, thereis no positional change in a person who stands still (person standingstill), and thus, it is not possible to construct a course model and toestimate a direction. Also, by a method of performing pattern matchingwith a database which is like a general pedestrian model of PTL 1, it isnot possible to estimate a direction when appearance, such as clothes, aphysique, or the like, of a person standing still is greatly differentfrom that of a person in the database.

However, in a case where an autonomous mobile apparatus such as a robotpasses through an environment crowded with people standing still, it isnecessary to estimate a direction in which a person standing stillstarts walking, in order to prevent the autonomous mobile apparatus fromhitting the person or blocking movement of the person even when theperson standing still suddenly starts walking. A direction in which aperson standing still starts walking often matches a direction of afoot. The person standing still starts to move to a side or a backwardof the foot for only about one or two steps. Thus, it is suitable todetect a direction in which a person starts to move by a direction of afoot.

A purpose of the present invention is to provide a method for estimatinga direction of a person standing still, which method makes it possibleto perform a safe movement control by estimating a direction, in which aperson standing still starts to walk, from a momentary single stillimage of the person standing still and by moving through a region inwhich the person is not likely to be hit.

Solution to Problem

To achieve the above purpose, the present invention includes the stepsof: detecting a boundary position between a foot and a lower leg of aperson in an image acquired by an imaging unit, the boundary positionbeing a substantial boundary part, in a lower limb, between the foot,which is a part from a malleolus to a tip part, and the lower leg;detecting a feature quantity which makes it possible to classify aground and a part other than the ground in the image; setting, in aperipheral region around the boundary position, a plurality of localregions having positional information and/or direction informationrelative to the boundary position, and determining whether each of thelocal regions is the ground or the part other than the ground by usingthe feature quantity unique to the ground; determining a foot regionfrom the local region determined as the part other than the ground; andestimating a direction of the foot of the person from the local regionclassified as the foot region and from the positional information.

Also, to achieve the above purpose, preferably in the present invention,the boundary position between the foot and the lower leg is specified byusing a distance sensor.

Also, to achieve the above purpose, preferably in the present invention,the distance sensor is parallel to the ground and measures a planesurface at a height of the substantial boundary part, in the lower limbof the person, between the foot and the lower leg.

Also, to achieve the above purpose, preferably in the present invention,the feature quantity of the ground is calculated based on a histogram ofdata in each pixel in the image.

Also, to achieve the above purpose, preferably in the present invention,each of the local regions, which is set in the peripheral region aroundthe boundary position between the foot and the lower leg, is a sectorwith the boundary position as a center.

Also, to achieve the above purpose, preferably in the present invention,when a distance between paired foot regions is smaller than apredetermined value and a difference in a feature quantity between thepaired foot regions is equal to or smaller than a predetermined value,the paired foot regions are determined as the foot regions of the sameperson.

Also, to achieve the above purpose, preferably in the present invention,a direction of the person is estimated based on the information held inthe local region which is included in the foot region of the sameperson.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a methodfor estimating a direction of a person standing still, which methodmakes it possible to perform a safe movement control by estimating adirection, in which a person standing still starts to walk, from amomentary single still image of the person standing still and by movingthrough a region in which the person is not likely to be hit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart for describing a step of estimating a directionaccording to an embodiment of the present invention.

FIG. 2 is a schematic configuration view illustrating a directionestimating apparatus according to the embodiment of the presentinvention.

FIGS. 3( a) to 3(c) are schematic appearance views illustrating thedirection estimating apparatus according to the embodiment of thepresent invention.

FIG. 4 is a flowchart for describing a method for estimating afoot-lower leg boundary position according to the embodiment of thepresent invention.

FIG. 5 is a view for describing a method for estimating a horizontalplane foot-lower leg boundary position according to the embodiment ofthe present invention.

FIG. 6 is a view for describing an example of a method for calculatingprojection according to the embodiment of the present invention.

FIGS. 7(1) and 7(2) are views for describing an estimation result of thefoot-lower leg boundary position according to the embodiment of thepresent invention.

FIG. 8(1) is a view and FIG. 8(2) is a chart, which are for describing amethod for extracting a feature quantity of a ground according to theembodiment of the present invention.

FIGS. 9(1) to 9(4) are views for describing a method for estimating afoot direction of a person according to the embodiment of the presentinvention.

FIG. 10 is a view for describing a local region according to theembodiment of the present invention.

FIG. 11 is a flowchart for describing processing for specifying a tiptoeregion in the embodiment of the present invention.

FIG. 12 is a configuration view illustrating a direction estimatingapparatus according to a different embodiment of the present invention.

FIGS. 13( a) and 13(b) are appearance views illustrating the directionestimating apparatus according to the different embodiment of thepresent invention.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be described with reference to thedrawings.

First Embodiment

FIG. 2 is a view illustrating a configuration example of a directionestimating apparatus 1 in which the present embodiment is mounted.

FIGS. 3( a) to 3(c) are appearance views of the direction estimatingapparatus 1.

In FIG. 2, the direction estimating apparatus 1 includes a digitalcamera 101, a laser scanner 102, a calculator 103, and an outputterminal 104. The digital camera 101 acquires a digital image G andtransmits the acquired digital image G to the calculator 103. The laserscanner 102 transmits a measurement value to the calculator 103. Thecalculator 103 estimates a direction of a person 201 based oninformation acquired from the digital camera 101 and the laser scanner102, and outputs a result as an electric signal to the output terminal104.

In FIGS. 3( a) to 3(c), the digital camera 101 is provided to an upperpart of a direction estimating apparatus 2. As illustrated in FIG. 3(b), the digital camera 105 is attached in an inclined manner tophotograph, from above, an object to be photographed. The laser scanner102 is provided to a lower part of the direction estimating apparatus 1.The calculator 103 is placed around a central part of the directionestimating apparatus 2 and connected to the output terminal 104 behindthe calculator 103.

With reference to the flowchart in FIG. 1, a method for estimating adirection of a person standing still according to the present embodimentwill be described.

In S1 in FIG. 1, a digital image G around a foot of the person 201 isacquired from the digital camera 101. Each pixel in the digital image Gincludes, as numerical data C, color information such as RGB intensity.By using an infrared camera, a stereo camera, a three-dimensionaldistance sensor, or the like as an imaging unit, temperatureinformation, distance information, or the like can be suitably used. Inthe present embodiment, the RGB intensity is used as the numerical dataC.

In S2, a position indicating a boundary part between a foot and a lowerleg (foot-lower leg boundary position O_(M)), in the image G, of aperson standing still in the image G is set. Processing in S2 isillustrated in a flowchart in FIG. 4.

In SS101, the laser scanner 102 scans a plane surface F302 parallel to aground T301, which is illustrated in FIG. 3( c), and a coordinate datagroup of a surface of the boundary part between the foot and the lowerleg of the person 201 is acquired.

As illustrated in FIG. 3( c), the height of the plane surface F302 isaround 15 to 30 cm, and the height around an ankle of a person issuitable thereto. In SS102, a representative position of a crosssectional surface of the boundary between the foot and the lower leg onthe plane surface F302 (horizontal plane foot-lower leg boundaryposition O′_(M)) is set from the coordinate data group acquired inSS101. As a method for the setting, there is a following method.

First, in the coordinate data group acquired by the laser scanner 102,coordinate data points are separated into groups by regarding adjacentcoordinate data points within a range of a certain distance ascoordinate data points of the same object. Then, as illustrated in FIG.5, in a case where a shape of the cross sectional surface of theboundary between the foot and the lower leg is regarded as a circle, acentral position of the cross sectional surface of the boundary is setas the horizontal plane foot-lower leg boundary position O′_(M).

For example, in a case where a coordinate data point group which belongsto a group k includes {d₁, d₂, d₃, and d₄}, three coordinate data points{d_(i), d_(j), and d_(k)} (i, j, and k are arbitrary natural numbers)are selected arbitrarily, and an intersection of perpendicularbisectors, each of which is formed by arbitrary two points among {d_(i),d_(j), and d_(k)}, is set as the horizontal plane foot-lower legboundary position O′_(M). In SS103 in FIG. 4, the horizontal planefoot-lower leg boundary position O′_(M) acquired in SS102 isprojectively transformed, and the foot-lower leg boundary position O_(M)in the digital image G acquired in S1 is calculated.

As illustrated in FIG. 6, when an imaging surface of a camera isregarded as a plane surface M303, an arbitrary point X (x, y) on theplane surface F302 can be projectively transformed into a point X′ (x′,y′) on the plane surface M303 which satisfy an equation 1.

$\begin{matrix}\left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 1} \right\rbrack & \; \\\left\{ \begin{matrix}{x^{\prime} = \frac{{a_{1}x} + {b_{1}y} + c_{1}}{{a_{0}x} + {b_{0}y} + c_{0}}} \\{y^{\prime} = \frac{{a_{2}x} + {b_{2}y} + c_{2}}{{a_{0}x} + {b_{0}y} + c_{0}}}\end{matrix} \right. & {{equation}\mspace{14mu} 1}\end{matrix}$

By determining real coefficients a₀, b₀, c₀, a₁, b₁, c₁, a₂, b₂, and c₂,a mapping relationship between the plane surface F302 and the planesurface M303 is derived. By reducing a denominator and a numerator onthe right-hand side, it can be regarded that the equation 1 includeseight independent variables.

Thus, by measuring four vertexes of a tetragon A′B′C′D′, which is arectangle ABCD on the plane surface F302 imaged onto the plane surfaceM303 as illustrated in FIG. 6, coordinates of four vertexes of therectangle ABCD being already known, and by solving simultaneousequations by substituting a coordinate of each of the vertexes ABCD andA′B′C′D′ into the equation 1, all coefficients can be calculated. Bycalculating a coefficient before activating an apparatus, projectivetransformation of an arbitrary point on the plane surface F302 onto theplane surface M303 is calculated. Thus, as illustrated in FIGS. 7(1) and7(2), it is possible to projectively transform the horizontal planefoot-lower leg boundary position O′_(M) calculated in SS102, and tocalculate the foot-lower leg boundary position O_(M) in the digitalimage G.

In S3 in FIG. 1, a feature quantity Q_(f) unique to a ground isextracted from the digital image G. A method for extracting the featurequantity will be described with reference to FIGS. 8(1) and 8(2).

Each pixel in the digital image G in FIG. 8(1) includes RGB intensity asa numerical value. When calculated, a histogram of the RGB intensity ofthe digital image G resembles FIG. 8(2). Since the ground occupies agreat part of the digital image G, a color in the vicinity of each ofthe peaks R_(m), G_(m), and B_(m) of RGB in the histogram in FIG. 8(2),is estimated as a color of the ground, and RGB intensity which satisfiesan equation 2 is set as the feature quantity Q_(f) unique to the ground.[Mathematical Formula 2]C _(f) ={C|R _(m) −ΔR _(m) <R<R _(m) +ΔR _(f)∩G _(m) −ΔG _(f) <G<G _(m) +ΔG _(f)∩B _(m) −ΔB _(f) <B<B _(m) +ΔB _(f)}  equation 2

ΔR_(l), ΔR_(r), ΔG_(l), ΔG_(r), ΔB_(l), and ΔB_(r) are arbitrary realnumbers and are set suitably according to a condition of the ground.Note that when Q_(f) is constant all the time, Q_(f) may be extracted inadvance and may be stored inside or outside the apparatus.

In S4 in FIG. 1, a local region D_(k) is set in order to find a regionincluding a foot (foot region) from a peripheral region of the foot(foot peripheral region E) in the digital image G. For example, asillustrated in FIG. 9(2), it is assumed that foot-lower leg boundarypositions O_(MR) and O_(ML) in right and left lower limbs are set by S2.First, the digital image G is projectively transformed, in a similarmanner to S2, onto a surface parallel to the ground, and a state of thefoot viewed from a vertical direction toward the ground is simulated.Here, projectively transformed image is regarded as G′, and projectionpositions of O_(MR) and O_(ML) are regarded as O″_(MR) and O″_(ML),respectively. Next, a region, which is sandwiched between a circlehaving a radius of r_(min) and a circle having a radius of r_(max) witha foot-lower leg boundary position O″_(MR) or O″_(ML) after theprojective transformation as a center, is regarded as the footperipheral region E. Then, from the foot peripheral region E, aplurality of local regions D_(k) is selected. Each of the local regionsD_(k) is set, in a fan shape as illustrated in FIG. 9(3), to includeinformation of a position or a direction relative to O″_(MR) or O″_(ML).

In the present embodiment, as illustrated in FIG. 10 and expressed in anequation 3, D_(k) is set according to an arbitrary direction θ_(k) withO″_(M) as a center.

$\begin{matrix}\left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 3} \right\rbrack & \; \\{{{D\left( \theta_{n} \right)} = {O_{M} + {se}}}{{however},{e = \begin{bmatrix}{\cos\;\theta} \\{\sin\;\theta}\end{bmatrix}},{{\theta_{n} - {\Delta\theta}} < \theta < {\theta_{n} - {\Delta\theta}}},{r_{\min} < s < r_{\max}}}} & {{equation}\mspace{14mu} 3}\end{matrix}$

r_(min), r_(max), Δθ, and the number of D_(k) are set suitably accordingto an environment.

In S5 in FIG. 1, each of the local regions D_(k) is evaluated anddetermined whether it is the ground. Among the pixels in each of thelocal regions D_(k), the number of pixels which satisfy a condition ofthe feature quantity Q_(f) is regarded as an evaluation value of thelocal region D_(k). It can be determined that the higher the evaluationvalue is, the more ground the region has. When the evaluation value islarger than a predetermined value, D_(k) is determined as the ground.When the evaluation value is smaller than a predetermined place, D_(k)is determined as a part of the foot, and a step goes to S6 and D_(k) isclassified as a foot region K {D_(q)} (q is natural number). Note thatin the present embodiment, the foot peripheral region E is regarded as acircle, and the local region D is regarded as a sector. However, apolygon, an ellipse, or the like can be selected suitably.

In S7 in FIG. 1, it is checked whether all D_(k) is evaluated. Whenthere is a local region D_(k) which is not evaluated yet, a step goesback to S4 and D_(k) which is not evaluated yet is evaluated.

In S8 in FIG. 1, a foot direction θ_(M) of an object M is estimated froma positional relationship between the local region D_(q) classified asthe foot region K and the foot-lower leg boundary position O_(M).

For example, in a case of FIG. 9(3), at a time point of S8, D_(p) (p=1,2, 3 . . . , 6) and D* are classified as the foot region K. D_(p) is aregion including a tiptoe (tiptoe region T), and D* is a regionincluding a lower leg (lower leg region L). A foot direction of a personis a direction of a tiptoe with the foot-lower leg boundary positionO_(M) as a basis, and thus, it is possible to identify a foot directionfrom a position of the tiptoe region T. An example of separation of thetiptoe region T and the lower leg region L will be described withreference to a flowchart in FIG. 11.

In SS201, grouping is performed and local regions D_(q), which belong tothe foot region K and are continuously adjacent, are separated into thesame group. In SS202, the number of groups is checked, and when thereare two or more groups, a step goes to SS203. A group in a directionclose to a front direction (−y direction in FIG. 9(3)) is determined asthe tiptoe region T. When there is only one group, a step goes to SS204,and the group is determined as the tiptoe region T. In SS205, an averagevalue in a direction θ_(p) which sets the local region D_(p) included inthe tiptoe region T is regarded as the foot direction θ_(M).

For example, in a case of FIG. 9(4), a direction which sets a localregion D_(Ln) having the foot-lower leg boundary position O″_(ML) as abasis is regarded as θ_(Ln), and an average value in θ_(Ln) is regardedas a foot direction θ_(ML) on O″_(ML). A foot direction θ_(MR) on thefoot-lower leg boundary position O″_(MR) is calculated in a similarmanner.

All the foot directions estimated in such a manner are output from theoutput terminal 104. Also, in S8, when a distance between O″_(ML) andO″_(MR) is smaller than a certain value L and predetermined featurequantities Q_(M) of the tiptoe regions D_(Ln) and D_(Rn), whichrespectively have O″_(MR) and O″_(ML) as centers, are close to eachother, the tiptoe regions D_(Ln) and D_(Rn) are determined as those ofthe same person and the average value in θ_(ML) and θ_(MR) may beestimated as the foot direction θ_(M) of the person 201. As the featurequantity Q_(M), a feature point coordinate or the like by an RGB colorhistogram or edge detection is used suitably. Thus, even when the imageG includes a plurality of people, it is possible to estimate a directionof each person independently.

In such a manner above, it becomes possible to estimate a foot directionof the person 201 from a single image without using a database.

Second Embodiment

In the present embodiment, an example of using a distance image will bedescribed.

In FIG. 12, a direction estimating apparatus 2 for a person standingstill according to the second embodiment is illustrated. In FIGS. 13( a)and 13(b), appearance views of the direction estimating apparatus 2 areillustrated.

In the direction estimating apparatus 2 in FIG. 12, description of apart having the same function with the configuration having the sameassigned signs and are illustrated in FIG. 2 and FIG. 3 which have beenalready described is omitted.

The direction estimating apparatus 2 illustrated in FIG. 12 includes astereo camera 105 as an imaging unit, and two digital images in which anobject to be photographed is viewed from different positions aretransmitted to a calculator 103. The calculator 103 calculates adistance, with a ground T301 as a basis, of an object in the images fromthe two digital images, and generates a distance image G_(3D). Then, thecalculator 103 estimates a direction of a person 201 by using distanceinformation as numerical data C included in each pixel.

In FIGS. 13( a) and 13(b), the stereo camera 105 is provided to an upperpart of the direction estimating apparatus 2 and photographs a stereoimage with two lenses. As illustrated in FIG. 13( b), the stereo camera105 is attached in an inclined manner to photograph, from above, anobject to be photographed. The calculator 103 is placed around a centralpart of the direction estimating apparatus 2 and connected to the outputterminal 104 behind the calculator 103.

A flow of processing in the second embodiment will be described withreference to the flowchart in FIG. 1. However, S4 to S8 are the samewith S4 to S8 of the first embodiment which has been described already,and thus, description thereof is omitted.

In S1, two digital images G₁ and G₂ are acquired from a stereo camera104.

In S2, the distance image G_(3D) is generated from the digital images G₁and G₂. The generation of the distance image G_(3D) is performed, forexample, by the following method. First, edge extraction or the like isperformed on a minute region a_(1n) in the digital image G₁, and afeature quantity s_(1n) is given thereto. Next, a minute region a_(2n)having a feature quantity s_(2n) which is the same with the featurequantity s_(1n) of a_(1n) is searched from G₂. Then, a distance z, to aminute region a_(kn) (k=1, 2) is calculated by an equation 4, and isregarded as a distance of a minim region a_(1n).

$\begin{matrix}\left\lbrack {{Mathematical}\mspace{14mu}{Formula}\mspace{14mu} 4} \right\rbrack & \; \\{z_{n} = \frac{f \cdot h}{g_{1n} - g_{2n}}} & {{equation}\mspace{14mu} 4}\end{matrix}$

Here, g_(kn) (k=1, 2) is a barycentric position of a_(kn), f is a focaldistance of a camera, and h is a space between two cameras. Byperforming the calculation on the whole digital image G₁, the distanceimage G′_(3D) from the camera can be obtained. The distance image G_(3D)with the ground T301 basis can be easily acquired from G′_(3D).

In S3, a foot-lower leg boundary position is specified. In the distanceimage G_(3D) acquired in S2, a pixel, in which a distance C is largerthan the height from the ground T301 to an ankle of a person and thedistance C is smaller than a predetermined height, is recognized as thefoot-lower leg boundary position of the person 201, whereby a foot-lowerleg boundary position in the image G₁ or G₂ can be specifiedimmediately.

In S4, a feature quantity Q_(f) of the ground is extracted. The featurequantity Q_(f) of the ground indicates that a distance is in thevicinity of zero and is expressed in an equation 5.[Mathematical Formula 5]C _(f) ={C∥C|<ε}  equation 5

ε is an arbitrary real number and is set suitably according to acondition of the ground. After S4, processing similar to that of thefirst embodiment is performed on the image G₁ or G₂, and thus, a footdirection of a person can be estimated.

Third Embodiment

In the first embodiment, when a plurality of colors is included in theground, there is a plurality of peaks in the histogram. In such a case,a color in the vicinity of each peak may be regarded as the featurequantity of the ground.

Fourth Embodiment

In the first, second, and third embodiments, in a case where the featurequantity of the ground varies depending on a position of each person, itis possible to correspond to the case by acquiring a feature quantity ofa region not including a foot of each person from a local image aroundthe foot of each person.

REFERENCE SIGNS LIST

-   1 direction estimating apparatus of first embodiment-   2 direction estimating apparatus of second embodiment-   101 digital camera-   102 laser scanner-   103 calculator-   104 output terminal-   105 stereo camera-   201 object person-   T301 ground on which object person actually stands-   F302 scan surface of laser scanner-   M303 imaging surface of digital camera-   G digital image-   C feature quantity of image-   Q_(f) feature quantity of foot contact surface-   O_(M) foot-lower leg boundary position of person-   D local region-   E foot peripheral region-   K foot region-   θ direction

The invention claimed is:
 1. A method for estimating a direction of aperson standing still, comprising the steps of: detecting a boundaryposition between a foot and a lower leg of a person in an image acquiredby an imaging unit, the boundary position being a substantial boundarypart, in a lower limb, between the foot, which is a part from amalleolus to a tip part, and the lower leg; detecting a feature quantitywhich makes it possible to classify a ground and a part other than theground in the image; setting, in a peripheral region around the boundaryposition, a plurality of local regions having positional informationand/or direction information relative to the boundary position, anddetermining whether each of the local regions is the ground or the partother than the ground by using the feature quantity unique to theground; determining a foot region from the local region determined asthe part other than the ground; and estimating a direction of the footof the person from the local region classified as the foot region andfrom the information.
 2. The method for estimating a direction of aperson standing still according to claim 1, wherein the boundaryposition between the foot and the lower leg is specified by using adistance sensor.
 3. The method for estimating a direction of a personstanding still according to claim 2, wherein the distance sensor isparallel to the ground and measures a plane surface at a height of thesubstantial boundary part, in the lower limb of the person, between thefoot and the lower leg.
 4. The method for estimating a direction of aperson standing still according to claim 1, wherein the feature quantityof the ground is calculated based on a histogram of data in each pixelin the image.
 5. The method for estimating a direction of a personstanding still according to claim 1, wherein each of the local regions,which is set in the peripheral region around the boundary positionbetween the foot and the lower leg, is a sector with the boundaryposition as a center.
 6. The method for estimating a direction of aperson standing still according to claim 1, wherein when a distancebetween paired foot regions is smaller than a predetermined value and adifference in a feature quantity between the paired foot regions isequal to or smaller than a predetermined value, the paired foot regionsare determined as the foot regions of the same person.
 7. The method forestimating a direction of a person standing still according to claim 6,wherein a direction of the person is estimated based on the informationheld in the local region which is included in the foot region of thesame person.